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   VI-MotionCueing &gt; <a href="motioncueing_vi-motioncueing_tuning.htm">VI-MotionCueing tuning in VI-DriveSim</a>&nbsp;&gt;</p>
      <h1 class="p_Heading1" style="page-break-after: avoid;"><span class="f_Heading1">Fourth Step: Inversion avoidance</span></h1>

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<p class="p_Normal">The “inversion avoidance” feature is useful to reduce the accelerations inversion caused by high pass filtering. The working principle is simple and is based on saturating the reference signals to the MPC procedure when an acceleration inversion is detected.</p>
<p class="p_Normal">&nbsp;</p>
<p class="p_Normal">In figure below the vertical DOF is analyzed, and the perceived acceleration on the vehicle (black solid line) and on the platform are compared:</p>
<p class="p_Normal">&nbsp;</p>
<p style="text-align: justify; text-indent: 0px; padding: 0px 0px 0px 20px; margin: 0px 0px 0px 0px;"><span style="font-size:10pt; font-family: 'Arial';color:#000000;display:inline-block;width:20px;margin-left:-20px">1.</span>No inversion avoidance, red solid line;</p><p style="text-align: justify; text-indent: 0px; padding: 0px 0px 0px 20px; margin: 0px 0px 0px 0px;"><span style="font-size:10pt; font-family: 'Arial';color:#000000;display:inline-block;width:20px;margin-left:-20px">2.</span>Inversion avoidance, blue solid line. Note that at about 49s, a perceivable inversion would occur using only the filtering preprocessing.</p><p class="p_Normal">&nbsp;</p>
<p class="p_Normal">The same method could be applied for longitudinal and lateral accelerations and for the yaw velocity. In addition to the proposed example, another very important advantage of “inversion avoidance” is to eliminate the typical annoying effect of receiving positive acceleration &nbsp;when releasing the brake pedal.</p>
<p class="p_Normal">&nbsp;</p>
<p class="p_Normal">Note that the movements of the platform is drastically modified by the “inversion avoidance” correction. The normal effect in the position behavior is to fairly increase the platform usage, hence a modification of the input gain is require in order to avoid to reach the limit, sacrificing the intensity of the accelerations given to the driver. “inversion avoidance” should be deselected when the driver repeat its action (i.e. sequence of braking or accelerations) w.o. allowing the machine to recover to its neutral position.</p>
<p class="p_Normal">&nbsp;</p>
<div class="p_Normal" style="text-align: center;"><div style="margin:0px auto 0px auto;width:788px"><img alt="&nbsp;Comparison of perceived vertical accelerations with and without inversion avoidance." title="&nbsp;Comparison of perceived vertical accelerations with and without inversion avoidance." width="788" height="492" style="width:788px;height:492px;border:none" src="mtncng_image16.png"/><p style="text-align:center"><span class="f_ImageCaption"><br/>
Comparison of perceived vertical accelerations with and without inversion avoidance.</span></p></div></div>
<p class="p_Normal">&nbsp;</p>
<p class="p_Normal">&nbsp;</p>
<div class="p_Normal" style="text-align: center;"><div style="margin:0px auto 0px auto;width:788px"><img alt="&nbsp;Comparison of vertical positions with and without inversion avoidance." title="&nbsp;Comparison of vertical positions with and without inversion avoidance." width="788" height="494" style="width:788px;height:494px;border:none" src="mtncng_image17.png"/><p style="text-align:center"><span class="f_ImageCaption"><br/>
Comparison of vertical positions with and without inversion avoidance.</span></p></div></div>

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